Gyroscope calibration and attitude control using MRP-based nonlinear observer

Abstract

This paper covers nonlinear observer design to calibrate error factors of gyro such as bias, scale factor and misalignment. In attitude estimation, gyro should be corrected and Kalman Filter has been widely used in this problem, but it is sensitive to initial guess. Here, nonlinear observer is constructed to resolve the stability of estimation using Lyapunov theorem. Nonlinear Observer has the stability regardless of any initial guess, thus it can replace the filter or provide a stable initial guess for the filter. Also, the controller is integrated with the designed observer and the closed loop system for attitude of the spacecraft is finally completed. The estimation error by observer can affect the stability of the closed loop, thus the effects are analyzed mathematically. The Modified Rodrigues Parameter(MRP), which is recently interested because of its low nonlinearity and non-constrained property, is used for observer and controller design. MRP’s properties permit simplifying the design without any constraint. The designed observer and the closed loop system are simulated to verify the validation.